JP2013003253A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for storing a plurality of tables of light projection timing in advance and suppress the shutdown of a device due to waiting of generating the tables of the light projection timing.SOLUTION: An optical scanner comprises: an optical scan section 2 which is formed so as to swing around two axes and is capable of two-dimensionally scanning a laser beam from a light source part 5; a drive section 3 which sets at least one of frequencies of respective driving signals for swinging in accordance with corresponding resonance frequencies around the axes to output the respective driving signals; a storage section 6 which has two areas capable of storing tables of light projection timing; a light source control section 7 which commands the light projection timing at the table in the one area; a deviation amount detection section 8 which detects at least one of deviation amounts of the frequencies of the driving signals for the respective resonance frequencies; a timing table generation section 9 which, when the deviation amount is larger than a first threshold, starts generating the table and allows the other area to store the table; a changeover section 10 which, when the deviation amount is larger than a second threshold, changeovers a table reading destination; and a frequency change section 4 which, when the deviation amount is larger than the second threshold, changes respective drive frequencies.

Description

  The present invention relates to an optical scanning device that performs Lissajous scanning with laser light within a target region.

  2. Description of the Related Art Conventionally, an optical scanning device that performs Lissajous scanning with laser light within a target region is known. As this type of optical scanning device, for example, a light source unit that projects pulsed laser light at a preset projection timing, an optical scanning unit that is configured by a two-dimensional galvanometer mirror, and an optical scanning unit are driven. (For example, refer to Patent Document 1), for example, light for measuring the distance to an object existing in the target region by Lissajous scanning of the laser light in the target region It is used as an optical scanning means such as a distance measuring device or a laser scanning projector.

  In this type of optical scanning device, for example, the driving unit drives the optical scanning unit at a driving frequency that is initially set together with the resonance frequency of each oscillation direction of the two-dimensional galvanometer mirror. Here, for example, when the ambient temperature of the optical scanning unit changes or the temperature of the optical scanning unit itself changes, the resonance frequency also changes. In this state, if the optical scanning unit is driven without changing the driving frequency, it is not efficient because it is driven in a state shifted from the resonance frequency. As a countermeasure against temperature fluctuation of this resonance frequency, in this type of optical scanning device, conventionally, the drive frequency of both oscillating shafts is changed to follow the resonance frequency of each oscillating shaft, and drive control is performed, The drive frequency of one oscillating shaft is changed following the resonance frequency, and the drive frequency of the other oscillating shaft is changed while maintaining the ratio to the drive frequency of one oscillating shaft. Control is in progress. In addition, the timing of projecting the laser light projected from the light source unit is initial so that, for example, laser light along a Lissajous scanning trajectory determined according to an initially set drive frequency can be irradiated to each pixel predetermined in the target region. Is set.

JP-A-7-175005

  By the way, in this type of optical scanning device, when the difference between the initially set drive frequency (initial value) and the new drive frequency changed following the resonance frequency that changes according to temperature is large, If the difference between the set drive frequency and the new drive frequency changed while maintaining the frequency ratio is large, there is a possibility that the intended pixel cannot be irradiated with laser light at the initially set light projection timing. Yes, the light projection timing must be changed. In this case, for example, a range in which the resonance frequency can fluctuate is set in advance, and a projection timing table is stored in advance for each of a plurality of different driving frequencies that are predetermined in the fluctuating range. It is conceivable that a new projection timing table can be generated following the changing resonance frequency.

  However, in the case of a configuration in which a plurality of projection timing tables are stored in advance, the memory capacity for storing the projection timing tables is increased, resulting in an increase in cost. Further, when the projection timing table can be generated, the calculation required for the projection timing table generation is more complicated than the calculation required for changing the drive frequency. Compared with the calculation time required for changing the drive frequency, the time becomes extremely long. As a result, although the drive frequency has been changed, there is a possibility that the light emission timing cannot be changed because the calculation has not been completed, so the interlock must be activated to stop the device. There is a risk that a situation will not occur.

  The present invention has been made paying attention to such a problem. In an optical scanning apparatus using Lissajous scanning, it is not necessary to prepare a plurality of projection timing tables in advance, and the projection timing table waits for generation. An object of the present invention is to provide an optical scanning device capable of suppressing the stoppage of the device.

  In the optical scanning device according to the present invention, the movable part having the light reflecting surface is formed to be swingable around each of the first axis and the second axis orthogonal to each other, and the light reflecting surface is formed by the swinging of the movable part. An optical scanning unit capable of Lissajous scanning the incident light within a target region, a first drive frequency that is a frequency of a first drive signal that causes the movable unit to swing around the first axis, and the movable unit. At least one of the second drive frequencies that is the frequency of the second drive signal that swings around two axes is set in accordance with the corresponding resonance frequency around the axis, and the first drive signal and the second drive signal are set. A drive unit that outputs to the optical scanning unit and swings the movable unit; a light source unit that projects a pulsed laser beam toward the light reflecting surface; and the laser beam that undergoes the Lissajous scan is the target region It is possible to irradiate each predetermined pixel Using the storage unit having two areas capable of storing the laser light projection timing table and the table stored in one of the two areas, the light projection timing is instructed to the light source unit. A light source control unit that performs a shift amount of the first drive frequency with respect to the first resonance frequency around the first axis of the movable unit and the second with respect to the second resonance frequency around the second axis of the movable unit. A deviation amount detection unit that detects at least one of the deviation amounts of the drive frequency, and the first drive frequency and the first value for generating the new table when the deviation amount is larger than a predetermined first threshold value. The generation of the new table is started based on the predetermined frequency for each of the two drive frequencies, and the generated new table is stored in the other area of the storage unit. A timing table generation unit, and when the deviation amount is larger than the first threshold value and larger than a predetermined second threshold value, the reading destination of the table for the light emission timing command of the light source control unit is set as the other reading destination. A switching unit that switches to a region, and a frequency changing unit that changes the first driving frequency and the second driving frequency when the deviation amount is larger than the second threshold value.

  According to the optical scanning device of the present invention, at least one of the shift amount of the first drive frequency with respect to the first resonance frequency around the first axis and the shift amount of the second drive frequency with respect to the second resonance frequency around the second axis is detected. Then, when the deviation amount is larger than a predetermined first threshold value, table generation is started based on the predetermined frequency for each drive frequency for generating a new table, and the generated new table is stored in the storage unit. When the shift amount is larger than the first threshold and larger than the predetermined second threshold, the reading destination of the table for the light emission timing command of the light source control unit is switched to the other area. Since each drive frequency is changed, the difference between the first threshold value and the second threshold value is appropriately set to a sufficient value (difference) corresponding to the time required to generate a new table. In addition to setting, it is possible to complete the table generating the deviation amount is started when it becomes larger than the first threshold value, until the deviation amount reaches the second threshold value. Therefore, the table of the projection timing and the change of each drive frequency can be performed at the same time. Therefore, even when the intended pixel cannot be irradiated with the laser beam at the preset projection timing, the projection timing table is awaited. It is possible to suppress the apparatus stop due to. Further, it is not necessary to store a plurality of projection timing tables in advance.

It is a figure which shows schematic structure of one Embodiment of the optical scanning device by this invention, and is a block diagram at the time of applying to an optical ranging device. It is a figure which shows the structure of the two-dimensional galvanometer mirror which is an example of the optical scanning part of the said embodiment. It is a figure which shows the bridge circuit comprised by the piezoresistive element for detecting the rocking | fluctuation angle of the said optical scanning part. It is a figure which shows the general frequency characteristic of a two-dimensional galvanometer mirror. It is a figure for demonstrating the detection principle of the 1st deviation | shift amount and the 2nd deviation | shift amount by the deviation | shift amount detection part of the said embodiment. It is a flowchart which shows the switching process of the table of the light projection timing in the said embodiment. It is a flowchart which shows the processing content of the table production | generation task of the light projection timing in the said embodiment. It is a flowchart which shows the change process of each drive frequency in the said embodiment. It is a figure which shows an example of the temperature-resonance frequency table of the said optical scanning part. It is a figure which shows another frequency characteristic of a two-dimensional galvanometer mirror.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an optical scanning device according to the present invention.
The optical scanning device 1 performs Lissajous scanning with pulsed laser light within a target region. In the following description, the optical scanning device 1 is described as a case where the optical scanning device 1 is used as an optical scanning unit of an optical distance measuring device that measures a distance to an object existing in the target region by performing Lissajous scanning with laser light in the target region. To do.

  The optical scanning device 1 according to the present embodiment includes an electromagnetically driven optical scanning unit 2, a driving unit 3 that inputs a driving signal to the optical scanning unit 2 and swings it, and a frequency changing unit 4 that changes the frequency of the driving signal. A light source unit 5 that projects pulsed laser light; a storage unit 6 that stores a table of laser light projection timing; and a light source control unit 7 that commands the light source unit 5 to project laser light projection timing; The shift amount detection unit 8 that detects the shift amount of the frequency of the drive signal with respect to the resonance frequency of the optical scanning unit 2, the timing table generation unit 9 that generates a new light projection timing table, the first switching unit 10a, and the first switching unit 10a 2 includes a switching unit 10 having a switching unit 10b and a reset unit 11.

  The optical scanning unit 2 is formed so that a movable part having a light reflecting surface can swing around each of the first axis and the second axis orthogonal to each other, and the movable part swings to the light reflecting surface. The incident light can be Lissajous scanned in the target region. As such an optical scanning unit 2, for example, a two-dimensional scanning semiconductor galvanometer mirror (hereinafter simply referred to as “two-dimensional galvanometer mirror”) described in Japanese Patent No. 2722314 proposed by the present applicant is used. it can.

FIG. 2 shows a configuration of a two-dimensional galvanometer mirror 20 as a specific example of the optical scanning unit 2.
The two-dimensional galvanometer mirror 20 includes a frame-shaped fixed portion 21, an outer movable portion 23a disposed inside the fixed portion 21 and supported by a pair of first torsion bars 22a and 22a so as to be swingable, and an outer movable portion. And an inner movable portion 23b supported by a pair of second torsion bars 22b and 22b, which are arranged inside 23a and orthogonal to the first torsion bars 22a and 22a in the axial direction. Here, the central axis of the first torsion bars 22a and 22a is the x-axis (first axis), and the central axis of the second torsion bars 22b and 22b is the y-axis (second axis).

  A light reflecting surface (mirror) 24 is formed at the center of the inner movable portion 23b, and a first drive coil 25a and a second drive coil 25b are formed at the peripheral portions of the movable portions 23a and 23b, respectively. The end of the first drive coil 25 a is connected to the first electrode terminals 26 a and 26 a formed on the fixed portion 21, and the end of the second drive coil 25 b is the second electrode terminal 26 b formed on the fixed portion 21. , 26b. In addition, a pair of first permanent magnets 27a and 27a for applying a magnetic field to the first drive coil 25a and a pair of second permanent magnets 27b and 27b for applying a magnetic field to the second drive coil 25b are opposed to each other with the fixing portion 21 in between. Has been placed.

  The two-dimensional galvanometer mirror 20 causes each of the movable parts 23a and 23b to pass through currents (for example, alternating current) flowing through the drive coils 25a and 25b and magnetic fields generated by the first permanent magnets 27a and 27a and the second permanent magnets 27b and 27b. Lorentz force acts. As a result, the inner movable portion 23b swings in a two-dimensional direction, and laser light incident on the light reflecting surface 24 is Lissajous scanned within the target region. In the following description, the resonance frequency around the x axis of the entire movable portion including the outer movable portion 23a and the inner movable portion 23b is referred to as a “first resonance frequency”, and the resonance frequency around the y axis of the inner movable portion 23b is referred to as “resonance frequency”. This is referred to as “second resonance frequency”.

  Returning to FIG. 1, the drive unit 3 drives the optical scanning unit 2 to swing, and includes, for example, a first drive circuit unit 31 and a second drive circuit unit 32. In the present embodiment, the drive unit 3 causes the first drive frequency, which is the frequency of the first drive signal that causes the outer movable unit 23a and the inner movable unit 23b to swing about the x axis, and the inner movable unit 23b about the y axis. The second drive frequency, which is the frequency of the second drive signal to be oscillated, is set in accordance with the resonance frequency around the corresponding axis, and the first drive signal and the second drive signal are output to the optical scanning unit 2 to be outside. The movable portion 23a and the inner movable portion 23b are swung.

  The first drive circuit 31 uses a first drive coil 25a via a first electrode terminal 26a, 26a at a first drive frequency set in accordance with a first resonance frequency of a first drive signal (for example, an alternating current). To supply. Similarly, the second drive circuit 32 has a second drive frequency (for example, an alternating current) set in accordance with the second resonance frequency and a second drive frequency via the second electrode terminals 26b and 26b. It supplies to the drive coil 25b. The first drive frequency and the second drive frequency are initially set in accordance with, for example, each resonance frequency of the optical scanning unit 2 in the initial state, and can be changed by a command from the frequency changing unit 4 as will be described later. Has been.

  In this embodiment, the characteristics of the phase difference with respect to the driving frequency shown in FIG. 5 described later of the two-dimensional galvanometer mirror 20 are the same as the phase difference of −90 ° and the driving frequency of the resonance frequency (1300 Hz in FIG. 5). A point-symmetric characteristic with a point as a symmetric point shall be shown.

  The frequency change unit 4 changes the first drive frequency and the second drive frequency based on the detection result of the shift amount detection unit 8. In the present embodiment, as described later, The first shift amount data that is the shift amount of the first resonance frequency with respect to the first drive frequency and the second shift amount data that is the shift amount of the second resonance frequency with respect to the second drive frequency are input. It is configured. Further, two threshold values are set in advance for the shift amount of one of the first drive frequency and the second drive frequency. In the present embodiment, two threshold values are set in advance for the second deviation amount. In the following description, the smaller threshold value for the second deviation amount is the first threshold value, and the larger threshold value is the second threshold value. Say.

  The frequency changing unit 4 changes the first drive frequency and the second drive frequency when the shift amount (that is, the second shift amount in the present embodiment) is larger than the second threshold value. Specifically, the frequency changing unit 4 adjusts each drive frequency by adjusting the first drive frequency to the actual first resonance frequency and adjusting the second drive frequency to the actual second resonance frequency. For example, the frequency changing unit 4 adds or subtracts the first shift amount and the second shift amount to the drive frequency of each drive signal output from the drive circuits 31 and 32, respectively, thereby changing the actual resonance frequency. The drive circuit 31 and 32 are instructed to calculate and change each drive frequency according to the calculated resonance frequency. The determination of whether to add or subtract each deviation amount is made, for example, based on a phase difference value (described later) detected by the deviation amount detection means 8.

  The second threshold value is used as a trigger for changing each drive frequency, and is also used as a trigger for changing (switching) the projection timing as will be described later. Here, when changing each drive frequency according to the actual resonance frequency, if there is a large difference between each new drive frequency and each drive frequency before the change, which is initially set, etc., the laser light in the target area Since the scanning trajectory changes greatly, if laser light is irradiated without changing the light projection timing in this state, there is a possibility that the intended pixel cannot be irradiated with laser light. Therefore, the second threshold value is a limit value (for example, several Hz) at which the intended pixel can be irradiated with laser light without changing each drive frequency and light projection timing in a situation where each resonance frequency varies due to temperature variation. ) Is set appropriately. In addition, the first threshold value is set to be smaller than the second threshold value, and as described later, the difference from the second threshold value is a sufficient value according to the time required for generating data of new light projection timing. Appropriately set to be (difference).

  The light source unit 5 projects pulsed laser light toward the light reflecting surface 24 of the light scanning unit 2 and includes, for example, a light source 51 and a light projecting optical system 52. The projection timing of the laser beam projected by the light source unit 5 is commanded by the light source control unit 7. The light source 51 is a laser diode, for example, and emits light according to a command from the light source control unit 7 to emit pulsed laser light. The light projecting optical system 52 includes, for example, a collimator lens, and converts the laser light emitted from the light source 51 into parallel light. The laser light projected from the light source unit 5 is reflected by the light reflecting surface 24 of the light scanning unit 2 and is subjected to Lissajous scanning in the target area. Laser light (reflected light) reflected by an object existing in the target region is reflected and scanned by the light reflecting surface 24. The laser light (reflected light) is received by, for example, the light receiving unit 12 (for example, a photosensor) of the optical distance measuring device. The The light reception timing of the reflected light by the light receiving unit 12 and the laser light projection timing of the light source control unit 7 are input to the distance measuring unit 13 of the optical distance measuring device. Thereby, the distance measuring unit 13 of the optical distance measuring device measures the distance to the object existing in the target region based on the time difference between the input light projection timing and the light reception timing. Thus, the optical scanning device 1 according to the present embodiment is used as an optical scanning unit of the optical distance measuring device.

  The storage unit 6 has two areas capable of storing a laser light projection timing table that allows laser light subjected to Lissajous scanning to be emitted to each pixel predetermined in the target area. The first region 61 and the second region 62 are provided. For example, in the initial state, the first area 61 stores a table of light projection timing that is initially set as will be described later, and is connected to the light source control section 7 via the second switching section 10b. 62 is connected to the timing table generation unit 9 via the first switching unit 10a, and is configured to be able to store a new light projection timing table generated in the timing table generation unit 9 as will be described later. .

  The light source control unit 7 instructs the light source unit 5 to project light using a table stored in one of the first region 61 and the second region 62, via the second switching unit 10b. The first region 61 and the second region 62 are connected to each other. For example, the light projection timing is determined in advance in a target region by laser light that is scanned along a Lissajous scanning trajectory determined according to each driving frequency that is initially set in accordance with each resonance frequency of the optical scanning unit 2 in the initial state. The initial setting is such that each pixel can be irradiated. In the initial state, the light source control unit 7 is connected to the first region 61 via, for example, the second switching unit 10b, and reads a projection timing table (initial data) stored in the first region 61. The light source unit 5 is configured to instruct the light projection timing.

  The shift amount detection unit 8 detects at least one of a first shift amount that is a shift amount of the first drive frequency with respect to the first resonance frequency and a second shift amount that is a shift amount of the second drive frequency with respect to the second resonance frequency. To do. In the present embodiment, the deviation amount detection unit 8 detects the first deviation amount and the second deviation amount. For example, the first deviation amount detection unit 81, the second deviation amount detection unit 82, and the first deviation amount shown in FIG. A first bridge circuit 83 and a second bridge circuit 84 are provided.

  The first deviation amount detection unit 81 is based on, for example, the phase difference between the first drive signal output from the first drive circuit 31 and the output signal (oscillation angle signal about the x axis) of the first bridge circuit 83. The first shift amount is detected. Similarly, the second shift amount detection unit 82 is, for example, the second drive signal output from the second drive circuit 32 and the output signal of the second bridge circuit 84 (a swing angle signal around the y axis). A second shift amount is detected based on the phase difference.

  As shown in FIG. 2, the first bridge circuit 83 includes, for example, P-type diffused resistors, as shown in FIG. 2, the first to fourth piezoresistive elements R1 formed near the roots of the fixing portions 21 of the first torsion bars 22a and 22a. To R4, and detects a tensile strain and a compressive strain caused by a rocking motion (twist) around the x axis. Then, as shown in FIG. 3, the first to fourth piezoresistive elements R1 to R4 are connected by wiring to form a bridge circuit (input voltage Vi, output voltage Vo). Similarly, the second bridge circuit 84 includes fifth to eighth piezoresistive elements R5 to R8 formed in the vicinity of the roots on the outer movable portion 23a side of the second torsion bars 22b and 22b by, for example, P-type diffusion resistors. A tensile strain and a compressive strain caused by a swinging motion (twisting) around the y axis are detected. The fifth to eighth piezoresistive elements R5 to R8 constitute a bridge circuit (input voltage Vi, output voltage Vo) as shown in FIG.

  For example, when the outer movable portion 23a and the inner movable portion 23b are inclined to one around the x axis, the first and fourth piezoresistive elements R1 and R4 are subjected to tensile stress and the second and third piezoresistive elements R2 and R3 are compressed. When the outer movable portion 23a and the inner movable portion 23b are inclined to the other around the x axis, each of the piezoresistive elements R1 to R4 receives a stress opposite to the above. The first to fourth piezoresistive elements R1 to R4 formed by P-type diffusion resistance increase in resistance value when subjected to tensile stress, and decrease in resistance value when subjected to compressive stress. Therefore, the first bridge circuit 83 outputs a voltage corresponding to the swing angle (swing angle) around the x axis as a sine wave. By monitoring the output voltage Vo by the first deviation amount detector 81, the swing angle around the x axis can be detected continuously. Similarly, by monitoring the output voltage Vo from the second bridge circuit 84 by the second shift amount detector 82, the swing angle around the y axis can be detected continuously.

  Here, the principle of detection of the shift amount by the shift amount detection unit 8 will be briefly described with reference to FIGS. 4 and 5 are diagrams showing the frequency characteristics of the galvanometer mirror. FIG. 4 shows the mirror swing angle (gain) with respect to the drive frequency. FIG. 5 shows the drive signal and mirror swing with respect to the drive frequency. The phase difference from the moving angle (signal) is shown.

  As shown in FIG. 5, when the galvano mirror is driven with a drive signal having the same frequency as its resonance frequency (here, 1300 Hz), the phase of the mirror swing angle (signal) with respect to the phase of the drive signal is A 90 ° phase difference occurs between the drive signal and the swing angle signal with a 90 ° delay. That is, when the phase difference between the drive signal and the mirror swing angle signal is not 90 °, the drive frequency and the resonance frequency of the galvanometer mirror do not match. It can be considered that the frequency characteristics (resonance frequency) of the galvanometer mirror shown in FIG. Since the frequency characteristics of the galvanometer mirror can be acquired in advance, the amount of deviation between the drive frequency and the actual resonance frequency of the galvanometer mirror (by detecting the phase difference between the drive signal and the swing angle signal) ( The amount of resonance frequency shift) can be grasped.

  By using the above detection principle, the first deviation amount detection unit 81 can detect the first deviation amount based on the frequency characteristic around the x-axis of the optical scanning unit 2, and the second deviation amount detection unit. 82 can detect the second shift amount based on the frequency characteristic of the optical scanning unit 2 around the y-axis. Specifically, the first deviation amount detection unit 81 has information (table or the like) of drive frequency-phase difference characteristics corresponding to FIG. 5 about the x axis of the optical scanning unit 2, and the first drive signal And the first shift amount (shift amount of the first resonance frequency) are detected from the phase difference between the output signal of the first bridge circuit 83 and the output signal (swing angle signal). Similarly, the second deviation amount detection unit 82 has information on drive frequency-phase difference characteristics about the y axis, and the second deviation amount is calculated from the phase difference between the second drive signal and the output signal of the second bridge circuit 84. (Shift amount of the second resonance frequency) is detected.

  The timing table generation unit 9 is configured so that, for example, data on the detection result of the shift amount is input from the shift amount detection unit 8. In the present embodiment, the first shift amount is determined in advance. When it is larger than the threshold value, that is, when the normal use area shown in FIG. 5 is exceeded, generation of a new table is started, and the generated new table is stored in the other area of the storage unit 6 (for example, the second area). 62). The new table is generated in advance for the first drive frequency for the new table generation (hereinafter referred to as “table generation first frequency”) and for the second drive frequency for the new table generation. It is configured to perform based on a predetermined frequency (hereinafter referred to as “second frequency for table generation”).

  Specifically, the timing table generation unit 9 reads the current second drive frequency information from the frequency change unit 4 or the like, and adds or subtracts a second threshold value to the second drive frequency, for example, to generate a table. The second frequency for use can be determined in advance, for example, before the calculation of the light projection timing table. The second frequency for table generation matches the actual second resonance frequency when the second deviation amount matches the second threshold value. The timing table generation unit 9 has, for example, a “first resonance frequency-second resonance frequency table” in which a second resonance frequency and a first resonance frequency that change according to temperature are associated with each other in advance. A first resonance frequency corresponding to the second resonance frequency (that is, the second frequency for table generation) obtained from the drive frequency and the second threshold value is obtained based on the “first resonance frequency−second resonance frequency table”, This first resonance frequency is predetermined as a table generating first frequency. In this way, the timing table generation unit 9 generates a table that matches each resonance frequency when the second deviation amount matches the second threshold value when the second deviation amount becomes larger than the first threshold value. Generation of a new projection timing table is started based on the first frequency for table use and the second frequency for table generation. When the second frequency for table generation is determined in advance, whether to add or subtract the second threshold is determined, for example, based on the phase difference value detected by the shift amount detection means 8. Further, for example, the timing table generation unit 9 is connected to the second area 62 in the initial state, and outputs and stores the data in the second area 62 when generation of a new projection timing table is completed. .

  Here, the first threshold value is smaller than the second threshold value, and the difference from the second threshold value is a sufficient value (difference) corresponding to the time (several seconds) required for generating a new projection timing table, for example, It is appropriately set so as to be about 2 Hz. As a result, a new table generation started when the second shift amount becomes larger than the first threshold is reached until the second shift amount reaches the second threshold (that is, within the table generation area shown in FIG. 5). Can be completed. The difference between the first threshold value and the second threshold value is 2 Hz as an example. However, the present invention is not limited to this. Set as appropriate.

  When the shift amount (that is, the second shift amount in the present embodiment) is larger than the second threshold, the switching unit 10 sets the reading destination of the projection timing command table of the light source control unit 7 to the other area. (For example, the 2nd field 62), for example, comprises the 1st change part 10a and the 2nd change part 10b.

  The first switching unit 10a is configured to connect the timing table generating unit 9 to one of the first region 61 and the second region 62 of the storage unit 6 in a switchable manner. For example, in the initial state, the first switching unit 10a is a timing table. The generation unit 9 is connected to the second area 62, and when the timing table generation unit 9 completes a new table generation, the data can be output to the second area 62. For example, the first switching unit 10a is configured to switch the connection destination of the timing table generating unit 9 in synchronization with the switching operation of the second switching unit 10b. For example, when the second switching unit 10b switches the connection destination of the light source control unit 7 from the first region 61 to the second region 62 as described later, the first switching unit 10a sets the connection destination of the timing table generation unit 9 to the first one. The second area 62 is switched to the first area 61. This prevents the light source control unit 7 from overwriting another light projection timing table to be generated next in the area accessed for the light projection timing command to the light source unit 4.

  The second switching unit 10b connects the light source control unit 7 to one of the first region 61 and the second region 62 of the storage unit 6 in a switchable manner. For example, in the initial state, the light source control unit 7 is connected to the first region 61. When the second deviation amount becomes larger than the second threshold, the second switching unit 10b receives the command to switch the connection destination from the timing table generation unit 9 or the like, for example, so that the connection destination of the light source control unit 7 is The area is switched from the first area 61 to the second area 62. Thereby, the light source control unit 7 reads a new table and instructs the light source unit 5 to specify a new light projection timing. In this way, the light projection timing can be switched instantaneously.

  In the reset unit 11, the storage unit 6 stores a new projection timing table in the other region (that is, the second region 62 if a new table is generated for the first time in the present embodiment). In this case, the new table is erased based on the detection result of the deviation amount detection means 8. Specifically, the reset unit 11 completes the generation of a new table, and the second shift amount is equal to or smaller than the first threshold value even though the table is stored (shown in FIG. 6 described later). In step S9: YES), it is determined that it is not necessary to store and hold a new table, and the data in the table is erased (reset). Thereby, it is possible to prevent unnecessary data from being stored.

  Next, the light projection timing switching operation and each drive frequency changing operation of the optical scanning device 1 having the above-described configuration will be described with reference to FIGS. 1 and 6 to 8.

First, based on FIG.6 and FIG.7, the light emission timing switching operation will be described.
As shown in FIG. 6, in step S <b> 1, the drive unit 3 outputs each drive signal at each drive frequency. At this time, the frequency changing unit 4 outputs information on the current driving frequency to the timing table generating unit 9.

  In step S2, the first deviation amount detector 81 detects the first deviation amount based on the phase difference between the first drive signal and the output signal of the first bridge circuit 83, and the second deviation amount detector 82 The second shift amount is detected based on the phase difference between the second drive signal and the output signal of the second bridge circuit 84. Then, the detection result of each shift amount and each phase difference are output to the timing table generation unit 9 and the frequency change unit 4. Each phase difference is used to determine the shift direction of each resonance frequency in steps S81 and S23 described later.

  In step S3, the timing table generation unit 9 determines whether or not the input second shift amount is larger than the second threshold value. When the second deviation amount is not larger than the second threshold value, the process proceeds to step S4.

  In step S4, the timing table generator 9 determines whether or not the input second shift amount is larger than the first threshold value. If the second deviation amount is larger than the first threshold value, the process proceeds to step S5. If the second deviation amount is not greater than the first threshold value, the process returns to step S2.

  In step S <b> 5, the timing table generation unit 9 determines whether or not new light emission timing data (hereinafter referred to as “timing table”) has been generated. This determination is made based on whether or not the timing table generated flag is ON. If it is determined that the timing table generated flag is not turned on (that is, not generated), the process proceeds to step S6. This timing table generated flag is turned on in step S85, which will be described later, and turned off in step S12.

  In step S6, the timing table generator 9 determines whether a new timing table is being generated. This determination is made based on whether or not the timing table generation flag is ON. If it is determined that the timing table generation flag is ON (that is, if it is being generated), the process returns to step S2, and if it is determined that the timing table generation flag is not ON (that is, if it is not being generated) ) Proceeds to step 7. This timing table generation flag is turned on in step S7, which will be described later, and turned off in step S84.

  Then, the timing table generation unit 9 turns on the timing table generation flag in step S7, starts the timing table generation task shown in FIG. 7 in step S8, and returns to step S2, in parallel with the generation task. Then, the determination process of steps S2 to S6 is performed until the timing table generated flag is turned ON (step S85).

  Here, the flow of the timing table generation task will be described in detail with reference to FIG. In step S81, the timing table generator 9 determines whether the absolute value of each phase difference input from each bridge circuit 83, 84 is smaller than 90 °. When the angle is smaller than 90 °, the second resonance frequency is shifted to the high frequency side, so the process proceeds to step S82, and the second threshold value is added to the current second driving frequency input from the frequency changing unit 4. The second frequency for table generation is determined, the first frequency for table generation is determined based on the second frequency for table generation and the “first resonance frequency-second resonance frequency table” that is previously stored, and the first frequency for table generation And a new timing table is calculated based on the second frequency for table generation. On the other hand, when the angle is larger than 90 °, the resonance frequency is shifted to the low frequency side, so the process proceeds to step S83, and the second threshold for table generation is determined by subtracting the second threshold value from the current second drive frequency. Similarly to step S82, the first table generation frequency is determined, and a new timing table is calculated based on the table generation first frequency and the table generation second frequency. When the calculation of the new timing table is completed in step S82 or step S83, the timing table generated in the storage unit 6 (the first region 61 or the second region 62) to which the light source control unit 7 is not connected. The data is stored, the process proceeds to the next step S84, the timing table generating flag is turned off, the process proceeds to step S85, and the timing table generated flag is turned on. With these steps S81 to S85, the timing table generation task is completed.

  Next, returning to FIG. 6, if it is determined in step S5 that the timing table generated flag is ON (that is, if it has been generated), the process proceeds to step S9. In step S9, the reset unit 11 determines whether or not the second deviation amount is equal to or less than the first threshold value. If the second deviation amount is not less than or equal to the first threshold value, the process proceeds to step S10. On the other hand, if the second deviation amount is equal to or smaller than the first threshold value, it is determined that it is not necessary to store and hold a new timing table, and the process proceeds to step S9 '. In step S9 ', the new timing table is deleted (reset), and the process proceeds to step S12 described later.

  In step S10, the timing table generation unit 9 determines again whether or not the second shift amount is larger than the second threshold value. If it is determined that the second shift amount is larger than the second threshold value, the second switching is performed. The unit 10b is instructed to switch the connection destination, and the process proceeds to the next step S11. On the other hand, if the second deviation amount is not greater than the second threshold value in step S10, the process returns to step S9 and waits for timing table switching until a determination of YES is made in step S10.

  In step S11, the second switching unit 10b switches the reading destination of the timing table for the projection timing command of the light source control unit 7 based on the command from the timing table generation unit 9, and the light source control unit 7 The table is read and a new light projection timing is commanded to the light source unit 5. During the switching operation of the second switching unit 10b, the first switching unit 10a switches the connection destination of the timing table generating unit 9 to a region opposite to the region to which the second switching unit 10b is connected. Then, after these switching operations, the process proceeds to step S12.

  In step S12, the timing table generation unit 9 turns off the timing table generated flag, and the series of timing table switching processing is completed. Then, the process returns to step S2, and the monitoring of each deviation amount is continued, and the timing table switching process is enabled at any time.

  In step S3, when it is detected that the second deviation amount is larger than the second threshold value before detecting that the second deviation amount is larger than the first threshold value or before the generation of a new table is completed. In step S4 ′, for example, a stop command is output from the deviation amount detection unit 8 to the light source unit 5, and the projection of the laser light from the light source unit 5 is stopped. The first threshold value is set to be smaller than the second threshold value, and the difference from the second threshold value is a sufficient value corresponding to the time (several seconds) required for table generation. For this reason, usually, before detecting that the second deviation amount is larger than the first threshold value, or before the generation of a new table is completed, it is detected that the second deviation amount is larger than the second threshold value. Although it is not determined as YES in step S3, it can usually occur when the ambient temperature of the device at the start of driving already exceeds the allowable temperature range of the device, for example, or during the generation of the light projection timing data. The system can be stopped by assuming that there is no instantaneous and excessive temperature change. It is not always necessary to provide steps S3 and S4.

  Next, each drive frequency changing process will be described with reference to FIG. Steps S20 and S21 are the same as steps S1 and S2 in FIG.

  First, in step S21, the drive unit 3 outputs each drive signal at each drive frequency. In step S <b> 22, the deviation amount detection unit 8 detects each deviation amount, and outputs the detection result and each phase difference to the frequency change unit 4 and the timing table generation unit 9.

  In step S23, the frequency changing unit 4 determines whether or not the input second shift amount is larger than the second threshold, similarly to step S10 in the timing table generating unit 9. Here, when the second deviation amount becomes larger than the second threshold value, the process proceeds to step S24, where the first deviation amount is added to or subtracted from the current first drive frequency, and the second deviation amount is added to the current second drive frequency. By adding or subtracting the amount, each actual resonance frequency is obtained, and each drive circuit 31, 32 is instructed to change each drive frequency in accordance with the obtained resonance frequency. Thereby, the drive frequency changing process is completed. On the other hand, if the second deviation amount is not greater than the second threshold value in step S23, the process returns to step S22, and each drive frequency is not changed until YES is determined in step S23.

  As described above, according to the optical scanning device 1 according to the present embodiment, the difference between the two large and small threshold values (first threshold value, second threshold value) is a sufficient value (difference) corresponding to the time required to generate a new table. Thus, the table generation started when the deviation amount becomes larger than the first threshold can be completed by the time when the deviation amount reaches the second threshold. Therefore, the table of the projection timing and the change of each drive frequency can be performed at the same time. Therefore, even when the intended pixel cannot be irradiated with the laser beam at the preset projection timing, the projection timing table is awaited. It is possible to suppress the apparatus stop due to. Further, it is not necessary to store a plurality of projection timing tables in advance.

  In the present embodiment, a description has been given of a case where two large and small threshold values are determined in advance for the shift amount of the second drive frequency. ) May be set appropriately in advance. In this case, when the first deviation amount is larger than the first threshold, the timing table generation unit 9 determines the first frequency for table generation based on the first drive frequency and the second threshold, and the first frequency for table generation And a second frequency for table generation is determined based on the “first resonance frequency−second resonance frequency table”, and a new table generation is performed based on the first frequency for table generation and the second frequency for table generation. When the first deviation amount is larger than the second threshold value set larger than the first threshold value, the timing table is switched and each drive frequency is changed. As described above, the first threshold value and the second threshold value may be determined in advance for the shift amount of one of the first drive frequency and the second drive frequency.

  In the present embodiment, the oscillation angle signal has been described using the output voltage of the bridge circuit configured by the piezoresistive element. However, the present invention is not limited to this, and the swing angle signal of the bridge circuit configured by the piezoresistive element is used. A signal other than the output voltage may be used. For example, as described in Japanese Patent Application Laid-Open No. 2004-78130 and Japanese Patent Application Laid-Open No. 2004-242488, the back electromotive force generated in the first drive coil 25a and the second drive coil 25b is detected, and this is detected as the x-axis. The swing angle signal about the rotation and the y-axis can be used. However, in this case, when the optical scanning unit 3 is driven with a drive signal having a frequency that matches the resonance frequency, the phase difference between the drive signal and the swing angle signal (back electromotive force signal) becomes 0 °. .

  Further, the first shift amount and the second shift amount may be detected based on the temperature of the optical scanning unit 2 or the vicinity thereof without using the swing angle signal. Although not shown, a temperature sensor for detecting the temperature of the optical scanning unit 2 or the vicinity thereof is provided, and the temperature of the optical scanning unit 2 or the vicinity thereof and the resonance frequency are associated with each other about the x axis and the y axis. “Temperature-first resonance frequency table (see FIG. 9A)” and “Temperature-second resonance frequency table (see FIG. 9B)” are stored in the drive unit 3. In this way, The drive unit 3 can detect (calculate) the first shift amount and the second shift amount by referring to the temperature-resonance frequency table based on the detection result of the temperature sensor.

  In this embodiment, the drive unit 3 sets each drive frequency according to the corresponding resonance frequency around the axis, and the shift amount detection unit 8 detects the shift amount for each drive frequency, and the frequency change unit. 4 has been described with the configuration in which each drive frequency is changed in accordance with the resonance frequency around the corresponding axis. However, the present invention is not limited to this, and the drive unit 3 corresponds to either the first drive frequency or the second drive frequency. The deviation amount detector 8 is set in accordance with the resonance frequency around the axis, and the deviation amount detection unit 8 detects the deviation amount of the first drive frequency and the second drive frequency set in accordance with the resonance frequency, and the frequency change unit 4. The configuration may be such that the first drive frequency and the second drive frequency are changed while maintaining these frequency ratios.

  In this way, when changing the frequency ratio while maintaining the first drive frequency together with the first resonance frequency, the first threshold value and the second threshold value are set for the first shift amount. In this case, for the first drive frequency, the frequency changing unit 4 adds or subtracts the first deviation amount to or from the first drive frequency of the first drive signal output from the first drive circuit 31 to obtain the actual drive frequency. The first resonance frequency is calculated, the first drive frequency is changed in accordance with the calculated first resonance frequency, and the second drive frequency is changed so that the frequency ratio with the first drive frequency does not change. It changes so that it may change according to the 1st drive frequency. Further, the timing table generation unit 9 determines the first frequency for table generation by adding or subtracting the second threshold value to the current first driving frequency, and the second frequency for table generation is the table generation first frequency. Based on the first frequency for table generation and the second frequency for table generation, a new projection timing table is generated based on the first frequency for table generation so that the frequency ratio to one frequency does not change. Configure to start.

  Similarly, when changing the frequency ratio while maintaining the second drive frequency together with the second resonance frequency, the first threshold value and the second threshold value are set for the second shift amount. In this case, the frequency changing unit 4 adds or subtracts the second shift amount to or from the second drive frequency of the second drive signal output from the second drive circuit 31 for the second drive frequency, The second resonance frequency is calculated, the second drive frequency is changed according to the calculated second resonance frequency, and the first drive frequency is changed so that the frequency ratio with the second drive frequency does not change. It changes so that it may change according to the 2nd drive frequency. The timing table generating unit 9 determines the second frequency for table generation by adding or subtracting the second threshold value to the current second driving frequency, and the first frequency for table generation is the table generation second frequency. Based on the first frequency for table generation and the second frequency for table generation, a new projection timing table is generated based on the second frequency for table generation so that the frequency ratio to the two frequencies does not change. Configure to start.

  In the present embodiment, the phase difference characteristic with respect to the drive frequency of the two-dimensional galvanometer mirror 20 shows a point-symmetric frequency characteristic with the point where the phase difference is −90 ° and the drive frequency coincides with the resonance frequency as a symmetric point. However, the present invention is not limited to this, and as shown in FIG. 10, a case may be shown in which asymmetric (astigmatism) frequency characteristics are exhibited between the low frequency side and the high frequency side with the resonance frequency as the center. In this case, as shown in FIG. 10, the first threshold value is appropriately set for each of the low frequency side and the high frequency side, and the second threshold value is also appropriately set for each of the low frequency side and the high frequency side, In the timing table generation unit 9 or the like, the determination of which threshold value (first threshold value, second threshold value) on the low frequency side or the high frequency side is used is determined by, for example, the value of the phase difference detected by the deviation amount detection means 8. To be configured.

  In this embodiment, an electromagnetically driven two-dimensional galvanometer mirror is used as the optical scanning unit 2, but the present invention is not limited to this, and the rotation axes of the two one-dimensional galvanometer mirrors are orthogonal to each other. The present invention can also be applied to the optical scanning unit 2 configured to be arranged as described above. Further, in this embodiment, an electromagnetic drive type is used as the drive method of the optical scanning unit 2, but the present invention is not limited to this, and various drive methods such as an electrostatic method and a piezoelectric method are used. It can be applied to the scanning unit 2.

  Furthermore, in the present embodiment, the case where the optical scanning device 1 is used as the optical scanning unit of the optical distance measuring device has been described. Can also be used.

DESCRIPTION OF SYMBOLS 1 ... Optical scanning device 2 ... Optical scanning part 3 ... Drive part 4 ... Frequency change part 5 ... Light source part 6 ... Memory | storage part 7 ... Light source control part 8 ... Deviation amount detection unit 9... Timing table generation unit 10 .. switching unit 11... Reset unit 23 a.
23b inside movable part (movable part)
24..Light reflection surface 61..First region (region)
62 .. Second region (region)

Claims (5)

A movable part having a light reflecting surface is formed so as to be swingable around each of the first and second axes orthogonal to each other, and the light incident on the light reflecting surface by the swinging of the movable part is within the target region. And an optical scanning unit capable of Lissajous scanning,
A first drive frequency that is a frequency of a first drive signal that swings the movable portion around the first axis and a second drive that is a frequency of a second drive signal that swings the movable portion around the second axis. A drive unit configured to set at least one of the frequencies in accordance with a corresponding resonance frequency around the axis, and to output the first drive signal and the second drive signal to the optical scanning unit to swing the movable unit; ,
A light source unit that projects a pulsed laser beam toward the light reflecting surface;
A storage unit having two regions capable of storing a table of projection timings of the laser light so that the laser light to be scanned by the Lissajous can irradiate each pixel predetermined in the target region;
A light source control unit that instructs the light source unit on the light projection timing using the table stored in one of the two regions;
The amount of deviation of the first drive frequency with respect to the first resonance frequency around the first axis of the movable part and the amount of deviation of the second drive frequency with respect to the second resonance frequency around the second axis of the movable part. A deviation amount detection unit for detecting at least one of the above;
When the deviation amount is larger than a predetermined first threshold, the new table is generated based on the predetermined frequency for the first driving frequency and the second driving frequency for generating the new table. A timing table generation unit that starts generation and stores the generated new table in the other area of the storage unit;
A switching unit that switches the reading destination of the table for the projection timing command of the light source control unit to the other region when the deviation amount is larger than the first threshold and larger than a predetermined second threshold;
A frequency changing unit for changing the first driving frequency and the second driving frequency when the deviation amount is larger than the second threshold;
An optical scanning device comprising: The drive unit sets the first drive frequency and the second drive frequency according to the corresponding resonance frequency around the axis, respectively.
The shift amount detection unit detects a shift amount of the first drive frequency with respect to the first resonance frequency and a shift amount of the second drive frequency with respect to the second resonance frequency,
The first threshold value and the second threshold value are determined in advance for the shift amount of one of the first drive frequency and the second drive frequency,
2. The light according to claim 1, wherein the frequency changing unit adjusts the first driving frequency to the first resonance frequency and changes the second driving frequency to the second resonance frequency. Scanning device. The drive unit sets one of the first drive frequency and the second drive frequency according to the corresponding resonance frequency around the axis,
The deviation amount detection unit detects the deviation amount of the first driving frequency and the second driving frequency that are set according to the resonance frequency,
The optical scanning device according to claim 1, wherein the frequency changing unit changes the first driving frequency and the second driving frequency while maintaining a frequency ratio thereof.   When the storage unit stores the new table in the other area, the storage unit includes a reset unit that erases the new table based on a detection result of the shift amount detection unit. The optical scanning device according to claim 1.   The deviation amount detection unit detects that the deviation amount is larger than the second threshold before detecting that the deviation amount is larger than the first threshold or before the generation of the new table is completed. 5. The optical scanning device according to claim 1, wherein when the laser beam is emitted, laser light projection from the light source unit is stopped.